Device for mixing plaster compounds and mixtures



Nov. 16, 1948. G. M. HOLLENBACK I 2,453,914

DEVICE FOR MIXING PLASTER COMPOUNDS AND MIXTURES V 2 Sheets-Sheet 1 Filed April 10, 1944 3 -\\v\\\ y//////// ////////////////ll {mum g is mam;

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NOV. 16, 1948. HOLLENBACK 2,453,914

DEVICE FOR MIXING PLASTER COMPOUNDS AND MIXTURES Filed April 10, 1944 2 Sheets$heet 2' lllllllll INVENTOR, 650, /7 #0; Emma/(- Patented Nov. 16, 1948 STATES ATENT OFFICE George M. Hollenback, Los Angeles, Calif.

Application April 10, 1944, Serial No. 530,298

2 Claims.

The present invention relates to methods and devices for mixing plaster mixtures or compounds. The device is particularly adaptable when the plaster so mixed is to be used for the purpose of making castings or molds for the casting of metal, or other substances requiring dimensional accuracy.

The invention is particularly adaptable for use by manufacturing dentists in the making of inlays, crowns, and other articles.

The invention has for an object the provision of a device capable of forming a plaster mixture or compound which is substantially free from air, and is smooth and dense in character, with the result that when the plaster is used for molding purposes, the casting will have a smooth dense surface free from pits and other imperfections. The device is inexpensive in cost of manufacture, and capable of producing superior results for the purpose intended.

With the above mentioned and other objects in view, the invention consists in the novel and useful provision, formation, construction, association, and relative arrangement of parts, members and features, all as shown in certain embodiments in the accompanying drawings, described generally, and more particularly pointed out in the claims.

In the drawings:

Figure 1 is a perspective view of the device as an entirety,

Figure 2 is a top plan view of the device,

Figure 3 is a sectional view on the line 33 of Figure 2,

Figure 4 is a transverse sectional view on the line 4-4 of Figure 8,

Figure 5 is a plan View looking in the direction of the arrow 5 of Figure 4,

Figure 6 is a bottom plan view looking in the direction of the arrow 6 of Figure 4,

Figure '7 is a side elevation of the cover and certain associated elements of the invention,

Figure 8 is a side elevation of the mixing bowl of the invention,

Figure 9 is a plan view looking in the direction of the arrow 9 of Figure '7,

Figure 10 is a flask or ring used in the practice of the invention, and

Figure 11 is a device which is adapted to carry the pattern and used in the practice of the invention.

Referring now to the drawings, I have, in Figure 1, shown the device as an entirety and in assembled form. This device includes a mixing bowl I which may be utilized as the member with- 2 in which the desired amount of plaster and water is placed and initially mixed in any approved manner, such as by a spatula. In the present instance, the mixing bowl is shown as being formed of semi-flexible rubber, although it is evident that other materials might be utilized. The device also includes a cover or cap 2, adapted to be fitted over the top of the mixing bowl, and which cap carries a means 3 for agitating the plaster within the mixing bowl. In addition, the cap supports means 41 constituting a vibratory member for causin the mixed plaster to move from the mixing bowl during one phase, in the use of the device. Means 5 is associated with cap 2, the said means effecting communication with the interior of the mixing bowl when the cap is placed thereover, and which means is associated with some form of vacuum producing device for the purpose of exhausting air from the plaster mixture within the bowl. A flask or ring 6 cooperates with the mixing bowl I and a former member I. The ring 6 is adapted to fit against a portion of the mixing bowl to receive the plaster mixture after said mixture has been thoroughly agitated, and to flow around a pattern carried by the former member 1, the pattern being positioned within the ring or flask.

As depicted by Figures 7, 8, 10 and 11, the device as an entirety has its several component parts shown separated. The mixing bowl may assume any configuration desired. The shape shown in Figures 4 and 8 is useful when the plaster used constitutes an investment material, such as used by dentists. The mixing bowl includes a curved side wall 8 provided with a rim flange 9 and a thickened base 10. This base has a central orifice or opening H communicating with a counterbore or opening of enlarged diameter 82. The base is formed with an annular groove 13, the construction providing as between opening l2 and said groove a thin annular wall [4. As before stated, the mixing bowl is adapted to have the plaster placed therein. If the plaster constitutes an investment material, the investment material is mixed with water by means of a spatula, while in the mixing bowl. To prevent the investment material from passing through the opening II, I may plug said opening with a cork or other means. The bowl is adapted to fit against the cap 2, while the investment material is being a itated by the means 3.

The cap 2 is provided with a rim flange l5, which overlaps the flange 9 of the bowl. The inner surface of the cap is provided with an annular depending bead it which indents a soft rubber gasket I! mounted on the flange 9 of the bowl. Obviously, this aids in sealing the cap against the bowl. The cap is provided with a central bore [8, within which bore is positioned a sleeve-type bearing Hi. This bearing is held to the cap in any approved manner, and the said cap is centrally reinforced by an annular top plate 20. Passed through the bearing is a shaft 2|. The shaft is provided with an enlarged head 22 formed with a kerf 23. Interposed between an end of the bearing sleeve l9 and the portion 24 of the head and surrounding shaft 2| is a resilient sleeve 25. The shaft is provided with means 26 for maintaining the shaft within the bearing IS. The means 3 for mixing the plaster constitutes a paddle secured to the shaft at 21. This is accomplished by splitting the end of the shaft and fitting the paddle therein, as see Figure 9. This .paddle is in the form of a semi-circular disc provided with edge notches 28, 29 and 3!]. The arrangement of the paddle is such as to fit closely within the mixing bowl so the plaster is smoothed in ribbon streams during the agitation or mixing caused by rotation of the paddle.

The means 4 constitutes in its simplest embodiment some device for vibrating the cover or cap 2, As illustrative of such a means, I have provided a clamp 3i secured to the sleeve bearing IS, the clamp carrying an outwardly extending shaft 32, upon which is mounted an ofi-center weight 33. This weight is provided with a kerf 34..

Part of the means includes a part having a nipple 35 secured to the cap 2 adjacent bore [8. Suitable means 3?, such as a rubber hose, secured to nipple 36, leads to a vacuum pump or other air exhausting means, indicated diagrammatically at 3,8.

The flask B constitutes an elongated tubular member which may be provided with a beveled edge 39.

The former 7 provides a base member for the flask and centrally carries a sprue pin 40. This sprue pin is embedded in a semi-spherical part 4!. It is also to be observed that the former is provided with three step portions 42, 43 and 44 of different diameter. When the bottom of the flask engages the former I, the base rests. upon the portion 43, while portions 4! and Mfit within the flask.

The operation, uses and advantages of the invention are as follows:

We assume that the material to be mixed is for dental purposes, and constitutes investment material. This material is a fine powder adapted to be mixed with water. The mixing bowl is first plugged by placing a cork or similarmeans in opening H, and thereafter the powder is placed in said bowl and water added, the entire mass be ing initially stirred by some means, such as a spatula. As the mixed material is relatively stifi or viscous after mixing, the plug may be removed from the opening H. The bowl is then brought into pressure engagement with cap 2, which will cause the bead l6 to indent gasket ll. The flask is then moved within the confines of wall I 4 and into end engagement with a gasket 45, followed by engagement with said flask of former member I. This former member carries on the sprue pin the desired pattern. It is intended that no air leakage should occur between the sprue pin and the former member I. The bowl is then placed under vacuum conditions by connecting the same with pressure reduction apparatus 38. This pressure reduction apparatus is not detailed,

as any type of pressure reduction apparatus will do. One type that I have employed includes a connection with a spigot so that as water is passed through said spigot, a suction results in the line communicating with the nipple 38. Under pressure reduction, the former member 1 is drawn tightly against the flask 6, the flask 6 held in sealing engagement with the bowl around the opening H, and the cover 2 sealed on the bowl and the entire investment material subjected to a vacuum condition. If now the paddle or agitator 3 is rotated within the bowl, the relatively stifif investment material is intimately mixed and smoothed in ribbon streams, and any air therein, such as air bells, is removed from said material. The agitator 3 is operated by engaging a conventional power drive (not shown) with the kerf 23 of the head 22 of the shaft 2|.

While the vacuum is being maintained, I then subject the entire device to a vibration by rapidly rotating means 4. This is accomplished by disconnecting the drive from the agitator 3 and connecting it to the vibrator 4 through engagement with the kerf 34 of the weight 33 on the shaft 32. This causes the investment material to pass through the opening H and into the flask 6 surrounding the pattern, sprue pin, and part 4| of member 7. After a given length of time, usually a few seconds, the investment material is entirely moved from the bowl into the flask, whereupon the vacuum may be broken, the cover 2 removed from the bowl, and the flask 6 separated from the bottom of the bowl. The investment material is allowed to harden. Upon removal of member 1 with its sprue pin, the pattern remains in the mold, but the pattern is readily removed by heating the mold, the pattern material passing through the sprue which has previously been formed by the sprue pin.

To make a casting, it is simply necessary to melt the material, such as gold, and pour it into 1e basin portion which has been formed by part 3! of member 7, the molten metal passing through the sprue and into the mold cavity.

Actual use of the present device has demonstrated and shown that accurate castings are made, the casting being hard and dense, with a smooth surface free from pits and imperfections or small openings, such as would be otherwise present if all air had not been removed from the investment material.

In some instances, it may be desired to make a plaster mix which is substantially free from, entrapped air. To do this, I need simply to plug the opening H and thereafter rotate the paddle while maintaining a sub-atmospheric condition within the bowl.

I claim:

l. A device of the character described including a mixing bowl having a discharge opening and in which a relatively stiff plastic mix is placed, a cover to seal said bowl, a rotatable paddle in the bowl conforming to the interior of the same, means to smooth the mix in ribbon streams during agitation caused by rotation of the paddle, means to maintain the sealed bowl under subatmospheric pressure, a flask in sealing engagement with the bowl and aligned with the discharge opening, and separate means to vibrate the bowl to discharge the mixed material therefrom into the flask while the bowl is still under sub-atmospheric pressure.

2. A device of the character described including a. mixing bowlin which a relatively stiff plastic flask while the same is still sealed to the bowl by sub-atmospheric pressure.

GEORGE M. HOLLENBACK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,741,646 Nielsen Dec. 31, 1929 1,751,097 Nelson et a1. Mar. 18, 1930 1,839,082 Burgard Dec. 29, 1931 2,165,466 Erdle July 11, 1939 2,183,763 Brown Dec. 19, 1939 2,192,902 Erdle Mar. 12, 1940 2,295,136 Stiers Sept, 8, 1942 2,344,754 Vang Mar. 21, 1944 

